Tapered fluid dynamometer

ABSTRACT

A DYNAMOMETER WHICH HAS A HOUSING PROVIDED WITH A FLUID INLET AND OUTLET AND ENCLOSING A SET OF INTERLEAVED STATOR AND ROTOR DISKS. THE DISKS ARE FABRICATED WITH WORK HOLES, THE RADIUS OF A CIRCLE INTERSECTING THE CENTERS OF SAID HOLES GRADUALLY INCREASING FROM THE DISKS ON THE INLET SIDE OF THE HOUSING TO THE DISKS ON THE OUTLET SIDE TO PROVIDE A CONE SHAPED CENTRIFUGAL FLOW OF FLUID THROUGH THE DYNAMOMETER.

1971 D. E. BARKER TAPERED FLUID DYNAMOMETER 5 Shoots-Shoot 1 Filed April1, 1970 INVENTOR.

DNARD E. BARKER QvkJrkJ TTORNEYS Nov. 9, 1971 D. E. BARKER 3,618,377

TAPERED FLUID DYNAMOMETER Filed April 1, 1970 3 Sheets-Shoot z ROTOR#1ROTOR FLOW HOLES WORK HOLES R E Q 33185 CI S'E LE $85. ASLEE Ha I 5.875I8 .500 3.750 I8 .625 4.750

2 6.250 I8 .562 3.875 I8 .687 5.l25 3 6.625 is .562 4.l25 I8 .750 5.5004 7.0 Is .625 4.375 l8 .8l2 5.875 5 7.375 is .625 4 .625 I8 .875 6.250 67.750 16 .687 4 .875 I8 .937 6.625

FIG. 4 U

G. I V INVENTOR.

DNARD E. BARKER A TORNEYS United States Patent 01 fice 3,618,377Patented Nov. 9, 1971 3,618,377 TAPERED FLUID DYNAMOMETER Dnard E.Barker, La Mesa, Califi, assignor to the United States of America asrepresented by the Secretary of the Navy Filed Apr. 1, 1970, Ser. No.24,779 Int. Cl. G01] 3/20 US. Cl. 73-134 11 Claims ABSTRACT OF THEDISCLOSURE A dynamometer which has a housing provided with a fluid inletand outlet and enclosing a set of interleaved stator and rotor disks.The disks are fabricated with work holes, the radius of a circleintersecting the centers of said holes gradually increasing from thedisks on the inlet side of the housing to the disks on the outlet sideto provide a cone shaped centrifugal flow of fluid through thedynamometer.

STATEMENT OF GOVERNMENT INTEREST The invention described herein may bemanufactured and used by or for the Government of the United States ofAmerica for governmental purposes without the payment of any royaltiesthereon or therefor.

BACKGROUND OF THE INVENTION The invention relates to dynamometers andmore specifically to a fluid dynamometer having a tapered diskconfiguration for distributing more evenly the power absorptionthroughout the stages of the dynamometer.

The uses of hydraulic dynamometers or water brakes for absorbing thepower developed by the rotating shafts of prime movers are well known.For the most part, the prior art devices of this type utilizedinterleaved stators and rotors of identical construction. That is tosay, that the diameter of a circle passing through the center of thework holes of each disk are the same for all the disks. With such aconstruction, under high speed operation encountered in the testing ofturbine shaft engines used in the US. Navy, the first stage of thedynamometer being adjacent to the water inlet does most of the powerabsorption work, with progressively less work being accomplished by theremaining successive dynamometer stages, the last several stages doingpractically no work. The theory of water dynamometer operation is basedon the absorption of power by converting it to heat which is absorbed bythe water. In the prior art designs, the first stage pushes the water tothe outer limits of the housing. Although the flow holes are used tokeep some of the water in the working holes area in the disks, the workabsorption is ineffective, since forcing the water into a pattern athigh speed operation tends to raise the water to steam temperature inthe first few stages. Once the water converts to steam, the dynamometerloses complete load capability in those stages that are affected. Thisresult occurs because the work holes arecylindrically disposed, and thewater flowing in a centrifugal path by rotation of the rotor is forcedto stop at each stator stage in order to pass through the work holes andso doing performs uncontrolled work.

SUMMARY OF THE INVENTION This invention increases the efliciency and thelife of the dynamometer by distributing the work, or power absorption,more evenly throughout all the dynamometer stages and in a controlledmanner. This is accomplished over the prior art devices by reducing thepower absorption capability in the first stage and forcing the remainingstages of the dynamometer in succession to assume an equal share of theload capacity.

These beneficial results are achieved by gradually increasing the boltcircle, that is, the diameter of a circle intersecting the centers ofthe Work apertures in successive disks commencing from the disk on theinlet side to the disk on the outlet side of the dynamometer housing. Inaddition to providing a conical configuration to the corresponding workholes on successive disks, a spiral configuration is achieved byradially indexing the work holes in successive disks a given angulardisplacement. This conical-spiral arrangement of the work holes thusconform generally to the flow of the working fluid, usually water, towhich is imparted by the rotors a conical-spiral flow by centrifugalforce. Thus the fluid is able to flow from one dynamometer stage to anadjacent stage without the necessity of a complete stop in its rotarymotion, as was the case in the prior art dynamometers.

STATEMENT OF OBJECTS OF INVENTION A principal object of this inventionis to increase the life of a fluid dynamometer by distributing its powerabsorption throughout the various stages of the dynamometer, and acorollary object is to eliminate instability in operation of thedynamometer and erosion caused by the water flushing to steam in anoverloaded stage.

Another important object is to enable a given size dynamometer toincrease the load capacity and thereby enable the testing of largerhorsepower engines.

Other objects and many of the attendant advantages of this inventionwill be readily appreciated as the same becomes better understood byreference to the following detailed description when considered inconnection with the accompanying drawings wherein:

FIG. 1 is a vertical cross-section of a six-stage dynamometer showingthe novel tapered configuration of the stators and rotor disks;

FIGS. 2 and 3 are side elevation views of No. 1 rotor disk and No. 6rotor disk, respectively, from the set of six rotor disks;

FIG. 4 is a table tabulating pertinent dimensions of all the rotor disksin the entire set;

FIGS. 5 and 6 are enlarged side elevation views of No. 1 stator disk andNo. 6 stator disk, respectively, of the set of six stators;

FIG. 7 is a table tabulating the pertinent dimensions of all the statordisks in the entire set; and

FIG. 8 is a side elevation view of a set of stator disks, partially insection, showing the conical-spiral disposition of the work holes, andfor clarity illustrating only one corresponding work hole in each of thesuccessive disks in the set.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawing wherelike numerals refers to a corresponding part throughout the variousfigures there is shown in FIG. 1 a basic Navy-designed six stagedynamometer or water brake 10.

All existing components of the illustrated dynamometer are ofconventional design except for the unique construction of rotor disks 12and stator disks 14, the details later to be described, which form theessence of this invention. In the illustrated embodiment are shown a setof six rotor disks, forming a six stage device. The dimensions of therotor and stator disks hereinafter described are taken from a modelactually tested with a US. Navy designated T64 Turbo Shaft enginedeveloping approximately 3,750 H.P. It is apparent that the number,dimensions and configuration of the rotor and stator disks can be variedto 3 accommodate specified requirements for the dynamometer.

Dynamometer comprises a housing 16 formed of a cylindrical casing 18being closed at the ends by an inlet bell end 20 and an outlet bell end22. Inlet bell 20 is provided with inlets 24 for the admission of thebrake fluid, usually water, to housing 16, and bell end 22 is providedwith outlets 26 for the discharge of the water. A shaft 28 is rotatablymounted in the housing on a pair of ball bearings 30 set in the bellends, the shaft being provided with a splined connection 32 for couplingto the prime mover, not shown.

The set of six rotor disks 12 are suitably keyed at 34 to shaft 28 forrotation therewith. The rotor disks are spaced apart from each other byany suitable means, such as an integral flanged hub portion 36, toaccommodate the stator disks 14 which are interleaved therewith.

The details of the set of rotor disks are illustrated in FIGS. 2 and 3;FIG. 2 illustrating No. 1 rotor disk and FIG. 3 illustrating No. 6 rotorrisk, the numbering system starting from inlet 24 and ending at outlet26 in the housing. FIG. 4 is a table specifying the dimensions andconfiguration of all six rotor disks in the set. The constructiondetails of the rotor and stator disks are generally similar, and thedetailed description of the rotor disks will apply to the stator diskswith exceptions noted, such as dimensions. As is seen from FIGS. 2-4,each rotor disk 12 may be provided with an annular group of work holes38 and an annular group of flow holes 40, each group concentricallyarranged, with the set of work hOles being outermost. As is well knownin the art, the operation theory of this type of dynamometer is theabsorption of power of converting the energy to B.t.u.s (raising thetemperature of the water flowing through the brake). This isaccomplished by the shearing of the water through the work holes. Theflow holes are used to pass the excess water from one stage to anotherto provide fluid for the succeeding stages. The diameters of all thework holes in each group on a given disk are identical, as are thediameters of all flow holes in each group on the same disk, although inmost instances the diameters between the holes in two groups on the samedisk will be different. In addition, the diameter of work holes and flowholes between the various disks will vary as can be seen from the chartin FIG. 4 where it will be noted that the diameters of both the workholes 38 and the flow holes 40 gradually increase in size on the disksfrom No. 1 through to No. 6.

In the illustrated embodiment, each rotor disk, as well as each statordisk as will be hereinafter noted, have 18 work holes and 18 flow holes,however, these numbers may be varied to tailor the dynamometer tospecific work requirements. The experimental results of one test inproviding different numbers of work holes and flow holes in successivedisks of the sets will be described under the heading operation.

An important feature of the novel disk design is the geometric patternof work holes 38 and flow holes 40 in the disks of the set. It has beenfound in practice that to achieve the objects of the invention, the boltcircles of both the work holes and the flow holes, i.e., the circlesintersecting the centers of the respective sets of holes, shouldgradually increase successively in all the rotor disks in the setcommencing from the No. -1 disk adjacent the inlet 26 through to the No.6 disk adjacent outlet 26, as can be observed from the table in FIG. 4.Likewise the diameters of each of the work holes 38 and the flow holes40 increase in diameter, as is also seen on the table, so that the workabsorption of the brake will be equalized throughout the six brakestages.

In addition, it is believed that by increasing the outer diameter of therotors from No. 1 to No. 6, giving the set a tapered configuration,assists in the equalizing of the work absorption of the brake stages.The successively increasing diameter of the bolt circles enable thelater stages of the brake to absorb more work than is possible underprior art configurations where all the respective bolt circles are ofthe same diameter. Thus, it is apparent that the holes in the six rotordisks will assume a conical or tapered configuration from the inlet tothe outside sides of the housing that generally conforms to the cone ofwater caused by the centrifugal force created by the rotors. By such adesign, coupled with the spiral pattern described in the followingdescription the water is able to move and advance from one stage to thenext without the necessity of a complete stop in its rotary motion ateach dynamometer stage. This provides better control of the loadcapability of each stage.

In addition to the above described tapered design, it was founddesirable to provide the holes of the rotors and stators with a spiralconfiguration with reference to the direction of rotor rotation. In thecase of rotors, the spiral arrangement increases water flow through thebrake if it is counterclockwise to the direction of rotor rotation,which as will be later observed is opposite to the spiral provided onthe stators. It is reasoned that after the water passes through the workholes in the stator the water lags because it is not moving as fast asthe next rotor and thus it passes through an after hole in the stator.

It has been found desirable on the model tested of the preferredembodiment that there be a 5 lag counterclockwise in each successiverotor of the set. This counterclockwise spiral constructionconfiguration is accomplished in the rotors of FIGS. 2 and 3 bysuccessively staggering each keyway 34 in the rotor disk 5 withreference to a given work hole 38. In FIG. 2, which illustrates rotor#1, keyway 34 is on a centerline 2 passing through the center of workhole 38a. In FIG. 3 which illustrates rotor 6 in the set, centerline 42passing through corresponding work hole 38 is displaced 25counterclockwise with reference to keyway 34, the intervening rotordisks, not illustrated, each lag 5 with respect to the disk immediatelyforward. It will be noticed in FIGS. 2 and 3 that the centers of workholes 38 and flow holes 40 maintain a uniform staggered relationship oneach disk.

As previously noted, the configurations of stator disks 14 are similarin many respects to the configurations of rotor disks 12, and thedifferences will be described. Stator disks 14 may be fabricated inhalves, as shown in FIGS. 5 and 6, to accommodate a split housing andare provided with oppositely disposed peripheral keyways 44 partially ineach half for assembly to a pair of corresponding keys 46 on the innerbore of split cylinder 18 (FIG. 1). A series of annular spacers 48 areprovided between the stator disks to perform two functions. First,spacers 48 lock the stators in spaced relationship with the rotor disks,and secondly, by decreasing the inner diameter of spacers 48 in directrelationship with the decreasing outer diameter of the rotor disks asubstantial uniform water volume as achieved in the various stages ofthe dynamometer. As is obvious from FIG. 1, the outer diameter of thestator disks must be of the same diameter to fit wihin casing 18,however, it is preferable that the inner diameters at 50 be increased ona corresponding tapered configuration from #1 to #6 stator in the set soas to allow a progressively larger passageway for a supply of water flowto move toward the rear of the brake without performing work, in asimilar manner as is performed by the flow holes in the stator dtISkS.This is to provide a supply of water for the rear s ages.

Referring to FIGS. 5-7 inclusive, there is shown in FIG. 5 a frontelevation view of stator #1 having an outer group of eighteen flow holes52 and an inner group of or ghteen work holes 54. Although the statorand rotor disks have the same number of holes in each set, thedimensions of the holes between the different disks of the set differare shown in the table of FIG. 7. Whereas the diameters of the flowholes and work holes on the rotor disks gradually rncrease from #1 to #6rotors as was seen in the table of FIG. 4, on the stator disks in FIG. 7the diameter of the flow holes decrease as the diameter of the workholes increase in dimensions, in order ot provide a controlled amount oftemperature rise in each stage to equalize the work performed therein.

Whereas the work holes and the flow holes in the rotors have acounterclockwise spiral, i.e., away from the direction of rotorrotation, in the stator disks the spiral of the work holes and flowholes are in an opposite direction, namely, in a clockwise rotation. Theclockwise spiral configuration on the stator disks is illustrated inFIG. 8 which discloses only one given work hole in each of the sixstator disks, the flow holes not shown for simplicity in illustration.

To provide the clockwise spiral configuration to the holes in the statordisks in FIGS. 5 and 6, the holes in each stator disk are advanced 5ahead in each succeeding stator disks, so that the holes in stator disk#46 will be 25 advanced with regard to the holes in stator #1 (justopposite to the lagging effect in the rotor disks described in FIGS. 2and 3).

In summary, as the spiral of the holes in the rotor disks arecounterclockwise and the spiral of the holes in the stator disks areclockwise, the combined spiral configuration of both disks is in effecta zig-zag pattern extending through the brake with the path beinggenerally in the direction of rotation of the rotor.

Operation The operation of the invention brake is quite similar to theoperation of a conventional brake in that the shearing action on thewater by the work holes in both disks raises the temperature of thewater and thus absorbs power by converting the energy into heat. It isimportant that there be a minimum pressure arise in the Water as itprogresses through the brake-just the opposite to the requirements of apump. It was found that the prior art problems of uneven distribution ofpower absorption and of erosion of the parts could be avoided byproviding a conical spiral path for the water as it flows through thebrake, and by controlling the distribution of water passing through thework holes by varying the size of the holes and the passageways throughthe cores of the stators.

A series of actual tests conducted on variations of the novel brakedesign with a T64 turbo shaft engine revealed some interesting results.

One attempt to create a spiral flow through the brake consisted ofincreasing the number of work holes and flow holes by one in eachsucceeding stage, i.e., from 13 in stator #31 to 18 holes in stator #6,and at the same time successively increasing the bolt circles of thegroup of holes. This necessitated that one hole one each stage he thestarting point therefore without spiral. After three hours of operation,upon disassembly a serious wear-pattern was found in that an erosioncaused by cavitation occurred at the spiral starting holes in the disksat the inlet stages. Although the total load capacity appeared to besatisfactory, the distribution among the stages was poor with the stagesnear the inlet taking most of the load. It was believed that the unequalnumber of holes in the disks actually upset the spiral condition of thewater since the erosion occurred on only one side of the disks.

Another test involved a brake design in which 18 holes used uniformlyfor all work holes and flow holes and on all stator and rotor disks. Theinner core diameter of all stator disks was the same. The followingresults Upon disassembly it was noticed that a similar erosion occurredaround the holes as the previous run test because the rotors wereinadvertently assembled backwards, providing an uneven flow through thebrake in a. similar manthis test are illustrated below in test #6.

Pressure Temperature low, Setting H.P. In Out In Out g.p.m.

Max. R 3, 170 98 98 70 165 161 -l 3, 000 92 95 70 160 156 2, 600 76 9870 155 148 2,050 55 67 75 155 117 Comparing the results in test #4 withtest #6 it can be seen that increasing the inner core diameter of thestators allowed more water flow and a greater workload capability. Withthe increase in water flow there was a substantial drop in the waterdischarge temperature which is most desirable.

Another test was conducted as test #6 to determine the eifect ofincreasing the diameter of work and flow holes by A The results areindicated below as test #8.

Pressure Temperature Flow, Setting H.P. In Out In Out g.p.m.

Max. R 3,110 67 62 70 150 180 Mil 970 70 55 70 145 173 Norm. R 2, 350 5850 70 145 146 1, 773 12 38 70 145 111 Comparing the results of test #8with test #6, increasing the diameter of both the' work and flow holeshad the desired effect of increasing the Water flow while decreasingboth the discharge temperature and pressure. The low dischargetemperature had the effect of causing a slight instability in the enginebut raising the water temperature by slightly closing the dischargevalve eliminated the unstability. If it is desired to increase the waterflow, the diameter of the stator flow hole could be increased slightlyto achieve this results.

From the above description, it has been shown how the efliciency of thewater brake can be increased which materially lengthens the operatinglife. In addition by more uniformly distributing the workload capabilityover all the stages of the brake, a larger rated prime mover can beaccommodated. As previously noted the number of work and flow holes,dimensions, number of stages may vary with each specific requirement.

In summary, the objects of the invention have been achieved by using atapered configuration in several aspects of the dynamometer. Firstly,the holes in the stator and rotor disks were designed along a taper i.e.conical-spiral to conform to the natural flow of water through thebrake. Secondly, the outer diameter of the rotor disks are tapered,thirdly, the inner core diameter of the stators are designed on a taperto provide an increased passageway for the non-working flow of water,and lastly, the spacers between the stator disks are tapered to maintaina uniform water volume in the various dynamometer stages.

Obviously many modifications and variations of the present invention arepossible in the light of the above teachings. It is therefore to beunderstood that within the scope of the appended claims the inventionmay be practiced otherwise than as specifically described.

What is claimed is:

1. A hydraulic dynamometer comprising:

a housing defining a generally cylindrical space having an inlet and anoutlet for the passage of a fluid;

a shaft journaled in said housing;

a set of rotor disks mounted on said shaft for rotation therewith;

a set of companion stator disks fixedly mounted interiorly on saidhousing;

the stator disks interleaved in spaced relation with the rotor disksforming a plurality of braking stages; said rotor disks and said statordisks each having a plurality of work apertures extending therethrough,the diameter of a circle intersecting the centers of said aperturesgradually increasing on successive disks commencing from the disks onthe inlet side to the disks on the outlet side of said housing;

whereby fluid passing through the housing from the inlet to the outletlet will move through the stages in a generally conical flow followingthe centrifugal force imparted to the fluid so that the power absorptionof the dynamometer will be distributed among all the several stages.

2. The dynamometer of claim 1 wherein each stator disk is provided withan inside diameter which increases in each successive disk from theinlet to the outlet side of the housng.

3. The dynamometer of claim .1 wherein the outer diameter of each rotordisks increase in each successive disk commencing from the inlet to theoutlet side of the housing.

4. The dynamometer of claim 3 wherein the stator disks are spaced apartby spacers, the inner diameters of the spacers vary directly with theouter diameter of the corresponding rotors to provide a conicalpassageway for the water through the housing.

5. The dynamometer of claim 1 wherein said disks have inner and outersets of concentric apertures extending therethrough, one set ofconcentric apertures comprising said work apertures and the other set ofconcentric apertures defining flow apertures.

6. The dynamometer of claim 5 wherein the outer set of concentricapertures on the rotor disks and the inner set of concentric apertureson the stator disks are work apertures.

7. The dynamometer of claim 6 wherein the corresponding apertures ofsuccessive disks are arranged to provide a spiral configuration.

8. The dynamometer of claim 7 wherein each disk has the same number ofapertures.

9. The dynamometer of claim 8 wherein the spiral configuration of thecorresponding apertures on successive disks is provided by angularlydisplacing each successive disk a given angular displacement.

10. The dynamometer of claim 9 wherein the spiral configuration of thecorresponding apertures in the stator disks extends in the direction ofrotation of the shaft, and the spiral configuration of the corrwpondingapertures in the rotor disks extends in a direction opposite to shaftrotation.

11. A hydraulic dynamometercomprising:

a housing defining a generally cylindrical space having an inlet and anoutlet for the passage of a fiuid;

a shaft joumaled in said housing;

5 a set of rotor disks mounted on said shaft for rotation therewith; theouter diameter of such disks gradually increasing in successive diskscommencing from the disk at the inlet to the disk at the outlet;

a set of companion stator disks fixedly mounted interiorly on saidhousing each having an inner diameter which gradually increases insuccessive disks commencing from the disk at the inlet to the disk atthe outlet, the stator disks spaced apart by a plurality of spacersforming with the interleaved rotors a plurality of braking stages, saidspacers having an inner diameter that increases gradually in directrelation to the outer diameters of the rotor disks forming a conicalwater passageway therewith;

selected rotor disks and said stator disks having a set of outer andinner circumferentially disposed work apertures respectively and a setof inner and outer flow apertures respectively extending therethrough,the diameter of a circle intersecting the centers of said aperturesgradually increasing on successive disks in each set from the disks oninlet side and extending to the disks on the outlet side of saidhousing;

the apertures on successive disks being staggered to provide a spiralconfiguration to the corresponding apertures in the disks of the set;

whereby fluid passing through the housing in the conical passageway fromthe inlet to the outlet will move through the stages in a generallyconical spiral flow following the centrifugal force imparted to thefluid so that the power absorption of the dynamometer will bedistributed among the several stages.

References Cited UNITED STATES PATENTS 1,718,175 6/1929 Nilson 73134 X1,854,952 4/1932 Nilson 73134 X 2,727,594 12/1955 Ganster, Jr 188-90FOREIGN PATENTS 834,897 9/1938 France 73--134 527,891 6/1931 Germany73-134 262,057 9/1949 Switzerland 188-90 CHARLES A. RUEHL, PrimaryExaminer US. Cl. X.R. 18890

